1. Field of the Invention
The present invention relates generally to a device for securing two or more items together. More particularly, the invention is an impact-fired pneumatic nailer having a disabling and enabling pneumatic operated safety mechanism.
2. Description of Related Art
Previously known safety systems for enabling/disabling the operation of a nailer typically comprise a feeler which is located on the underside of the body so that the nailer will operate only when the mouth of the nailer is pressed against the workpiece. This arrangement is particularly unacceptable for use in installing tongue and groove flooring because the fastener is driven through the tongue of the flooring and into the sub-floor at an angle. Accordingly, a conventional safety system will not always enable the nailer to drive a fastener. More importantly, however, the safety system may inadvertently be disengaged, thereby enabling operation of the nailer, by contacting the feeler with an object other than the workpiece, such as the user's foot or knee.
Dion, U.S. Pat. No. 4,907,730, discloses a pneumatic nailing tool operated by an impact from a hammer. The Dion nailer is provided with a needle valve that is biased outwardly from the base of the nailer. With the needle valve extended, compressed gas provided from an external source through an inlet port travels through a pair of passageways into a reservoir above closure disc until the pressure in reservoir is substantially equal to the pressure in reservoir. As a result, with the closure disc in position, the first exhaust passage is closed by a seal provided on trigger, and the second exhaust passage is open to the atmosphere, providing a safety system. The requirement that the needle valve must be retracted to operate the nailer is a safety feature to prevent inadvertent firing of the nailer. The requirement that the trigger must be impacted by hammer while the needle valve is retracted is a secondary safety feature of the Dion patent. The safety systems disclosed in the Dion patent does not prevent accidental firing of the nailer in the event of a multiple strikes.
Siegmann, U.S. Pat. No. 4,165,676, discloses a firing safety for a pneumatic nailer or stapler which cannot initiate a second cycle of the working piston even if the trigger and/or a nose piece sensor safety remain actuated. The firing safety includes a safety valve comprising an O-ring seal that seals the chamber from atmosphere when the safety valve is in the operative position. A trigger valve is movable within a valve sleeve to open and close a passageway that is in fluid communication with a pressure chamber. When the trigger valve is actuated, pin moves upwardly to seal passageway and chamber from the pressurized gas in reservoir. If safety valve is actuated, the pressurized gas in chamber and chamber exhausts to atmosphere, thereby permitting inlet valve to rise and initiate the working stroke of the cylinder. The working cylinder, however, remains in its lowermost position as long as trigger valve is actuated, therefore valve pin seals chamber from the pressurized gas in the reservoir. Accordingly, even repeated actuation of the safety valve does not result in a subsequent working cycle until the trigger valve has been released and re-actuated.
Siegmann, U.S. Pat. No. 4,194,664, discloses a pneumatic nailer or stapler including an inlet valve for supplying compressed air to a working piston which drives a fastener. A manually operated safety valve positioned in the passageway closes an opening provided in the passageway to atmosphere when actuated. As long as the safety valve is not actuated by an operator, pressurized gas in the passageway is exhausted to atmosphere even if the trigger valve is actuated. Thus, two separate actions, namely movement of the safety cap and the trigger lever, are required to initiate a cycle of the working piston.
Fehrs, U.S. Pat. No. 4,351,464, discloses a pneumatic fastener driving tool including a manually actuated release lever which, in conjunction with a pilot release valve connected to a workpiece contact sensor, controls the supply of compressed air to the working piston. An operator actuates lever with contact sensor. Only then is the compressed air in reservoir permitted to flow into pressure chamber through bore to raise the slide rod upwards into contact with the underside of the locking pin.
Tutomu, U.S. Pat. No. 4,384,668, discloses a safety system for a pneumatic impact tool, such as a nailer, for driving a fastener that prevents accidental injury which can occur at the instant that the tool is connected to a compressed air source. The safety system is automatically engaged when the tool is disconnected from the compressed air source, and must be manually disengaged before the tool can be used to drive a fastener. The safety system includes a safety valve piston reciprocally mounted in a safety valve cylinder. The safety valve piston is automatically moved to the top dead center position when the compressed air source is activated. To disengage the safety system, the operator must manually move the safety valve piston by manipulation of the unlocking knob to the bottom dead center position. In this position, communication between the first control air passage and the second control air passage is established so that air pressure in the control chamber is available to the trigger valve to control the operation of the nailer.
Haytayan, U.S. Pat. No. 5,645,208, discloses a pneumatic fastener driving apparatus provided with a pneumatic safety mechanism to prevent accidental firing of the tool. The apparatus includes a safety interlock valve comprising a mechanical locking member that is movable pneumatically between a first trigger-locking position and a second trigger-unlocking position when a safety rod is retracted.
Klaus, U.S. Pat. No. 4,509,668, discloses a pneumatically operated fastener driving tool including a safety device to prevent operation of the tool until a safety nose that is normally extended is in engagement with the workpiece. The tool includes a first valve that controls the flow of compressed air to the driving piston and a second valve that controls the flow of air to the safety mechanism. The trigger initially opens the second valve to extend the safety nose, and subsequently effects operation of the first valve once the safety nose engages the workpiece.
Bent, U.S. Pat. No. 4,540,110, discloses a pneumatic bone stapler including means for releasably latching the driver in its load position so that a user cannot inadvertently fire a staple. The latching means automatically engages the driver with the housing on return to the load position from the eject position of the driver. A manually actuated button is provided on the housing for releasing the latching means to permit movement of the driver to the eject position.
Halbert, U.S. Pat. No. 4,726,504, discloses a pneumatically operated, portable, self-piercing riveting apparatus including a plurality of links. The links serve as a locking means to prevent operation of the apparatus when the ends of the links are aligned in a co-linear relationship. In such position, a force applied to the anvil by the apparatus driver is not transmitted to the actuator. The apparatus does not drive a self-piercing rivet unless the user positions the links out of alignment.
Existing mechanically operated safety devices for pneumatic nailers are prone to an accidental firing from a unintentional multiple or "double-strike by the operator. A "double-strike" occurs after a nail has been intentionally discharged from the pneumatic nailer. If no mechanically operated safety device is in place or is bypassed in some manner, an unintentional discharge can occur by accidentally firing the nailer's trigger which will cause the pneumatic nailer to fire another fastener. As a result, serious injury can occur to the operator of the tools or to others nearby.
A need, therefore, exists for a pneumatic nailer that has a safety mechanism for preventing an accidental firing of the nailer in the event of multiple, unintended striking of the nailer by the operator.